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Highlights • Water for energy sector in China's two biggest megalopolises was analyzed. • Energy sector in Jing-Jin-Ji had 2.41 km3 of water withdrawal footprint in 2010. • Energy sector in Yangtze Delta had 9.59 km3 of water withdrawal footprint in 2010. • Water consumption footprint was 848.06 and 973.91million m3 respectively. • Jing-Jin-Ji had much larger external water footprint than Yangtze Delta. Abstract Using a consumption-based Multi-Regional Input-Output (MRIO) model, we investigate the distinctive characteristics, self-efficiency or external dependency, of energy demand's water footprint in China's two biggest and fastest developing megalopolises. We find that energy demand water footprint in the Jing-Jin-Ji and the Yangtze Delta amounted to 2.41 and 9.59 billion m³of water withdrawal respectively in 2010, of which 848.06 and 973.91 million m³was consumed. Among all energy products, electricity contributed the largest share to the energy sector's water footprint in both regions. The sectoral distribution of water footprint in the upstream supply chain differed by region. Most significantly, the agricultural sector accounted for more than 30% of water consumption footprint. In addition to water used locally, final energy demands in these two regions induced external water footprint beyond their administrative boundaries. The Jing-Jin-Ji region's energy sector had a smaller water footprint compared to the water-abundant Yangtze Delta region. However, external water footprint occupied a larger proportion in the former. Such divergence can be attributed to the distinctive water endowments and water-using technologies utilized in their respective energy sectors. Bespoke urban governance and policies tailored to local resource and technology portfolios are recommended for different urban agglomeration energy and water flows. [ABSTRACT FROM AUTHOR]

Water consumption in thermoelectric and hydropower plants in China increased from 1.6 and 6.1 billion m 3 , respectively, to 3.8 and 14.6 billion m 3 from 2002 to 2010. Using the concept of virtual water, we attribute to different electricity users the total water consumption by the electric power sector. From 2002 to 2010, virtual water embodied in the final consumption of electricity (hereinafter referred to as VWEF) increased from 1.90 to 7.35 billion m 3 , whilst virtual water in electricity used by industries (hereinafter referred to as VWEI) increased from 5.82 to 11.13 billion m 3 . The inter-provincial virtual water trades as a result of spatial mismatch of electricity production and consumption are quantified. Nearly half (47.5% in 2010) of the physical water inputs into the power sector were virtually transferred across provincial boundaries in the form of virtual water embodied in the electricity produced, mainly from provinces in northeast, central and south China to those in east and north China. Until 2030, VWEF and VWEI are likely to increase from 5.27 and 14.89 billion m 3 to 7.19 and 20.33 billion m 3 , respectively. Climate change mitigation and water conservation measures in the power sector may help to relieve the regional pressures on water resources imposed by the power sector. [ABSTRACT FROM AUTHOR]

The North China Grid has the highest proportion of fossil fuel-based electricity generation in China and also suffers from severe water scarcity issues. This study uses a multi-objective optimization model to explore future configurations of generating and cooling technologies of the electric power sector in the North China Grid subject to constraints imposed by existing policies on water conservation and carbon reduction in 2030. Our findings highlight that the current carbon reduction commitments of China do not have significant impacts on the North China Grid's electric power sector development while policies in the water sector generate much larger impacts. Imposing water constraint according to the 'Three Red Line' Policy requires increasing utilization of wind power and air cooling systems, which simultaneously increases economic cost and carbon emissions compared to the business as usual scenario. Imposing enhanced carbon emission and water consumption constraints reap the co-benefits of carbon reduction and water conservation by increasing the proportion of solar PV generation to 8.21%, which increases the unit electricity cost from RMB 0.82 per kWh to RMB 1.37 per kWh. In 2030, electricity generation in the North China Grid generates 1599.88 to 1690.89 million tons (Mt) of carbon emissions under different scenarios whereas imposing water constraint reduces water consumption from 3.34 billion m3 to 1.94 billion m3. Unlabelled Image • China's current carbon targets do not affect the development of the North China Grid. • Water sector policies have much larger impacts on the North China Grid. • Capping water use increases carbon emissions from the North China Grid. • Imposing both water and carbon constraints can realize co-benefits but at higher costs. [ABSTRACT FROM AUTHOR]

• Megacity water resource network should include physical and virtual water supply. • Input-output analysis is used to analyze megacity water vulnerability. • Megacities were more vulnerable to external than internal water scarcity. • Virtual water inflow help decrease vulnerability in water stressed megacities. The water resource networks that provide water for urban consumption consists not only of physical water supply, but also water embodied in imported goods and services i.e. virtual water supply or external water footprint. However, it remains unknown that if relying on external water footprint will increase or decrease the vulnerability of cities' water resource networks. Here, we evaluate the vulnerability of urban water resource networks for China's six megacities i.e. Beijing, Tianjin, Shanghai, Chongqing, Guangzhou, and Shenzhen. The vulnerability index was developed through combining a refined multi-region input-output table with both water footprint and water scarcity footprint analysis. The results showed that megacities need to import large volumes of virtual water embodied in food related sectors to balance their physical water shortages. The external blue water footprint (BWF) of the six megacities accounted for 80.7% of their total BWF, and was almost twice their physical water supply. The large share of external BWF helped Beijing, Tianjin, and Shanghai, which suffer extreme water stress in their urban areas, to decrease their total vulnerability by 39%, 33%, and 28% respectively, but conversely increase their vulnerability to external water shortages i.e. indirect vulnerability. Establishing megacity physical and virtual water resource networks based on input-output analysis provides an opportunity for urban water planners to internalize the risk of their external water footprint. Avoiding import water-intensive products from regions suffering extreme water stress, or managing indirect vulnerability through cooperation with those regions are suggested as viable water management approaches. [ABSTRACT FROM AUTHOR]

With the proliferation of electric vehicles (EV), large amounts of retired batteries need to be disposed, which poses emerging waste management challenges. Remanufacturing LIBs with materials recycled from used batteries is gaining increasing appreciation. Its environmental and economic benefits are still controversial and merit further examinations. This paper employs a life-cycle model and a process-based cost model to evaluate the greenhouse gas (GHG) emissions, water consumption, and the related costs of remanufacturing LIBs within the context of China, which is the biggest EV producer. Four types of LIBs, i.e. NCM 111 , NCM 622 , NCM 811 and NCA, and three different recycling methods, i.e. Pyrometallurgical Recycling (PR), Hydrometallurgical Recycling (HR), and Direct Physical Recycling (DPR) are analyzed. The environmental impacts of remanufacturing LIBs are assessed at both national and provincial levels. Results show that compared with manufacturing LIBs with virgin materials, remanufacturing LIBs can significantly reduce GHG emissions, water consumption, and production costs. Among the three recycling methods, DPR has the biggest potentials for reducing GHG emissions, water consumption, and manufacturing costs with 29.27%–38.15%, 30.07%–41.19%, and 25.61%–36.63% reduction, depending on the different types of LIBs. Regarding battery technologies, remanufacturing NCM 111 cell with DPR induces the least negative environmental impacts. Sensitivity analyses show that there are still large profit margins for remanufacturing LIBs with DPR process to bear the used LIB purchase price increase. Potential water-carbon conflicts are demonstrated for developing LIB remanufacturing industry due to different provincial electric power portfolios, which should be considered in future industry planning. [Display omitted] Environmental impacts and economic costs of remanufacturing EV LIBs are evaluated Direct physical recycling cuts manufacturing cost by 25.6–36.6% Direct physical recycling reduces GHG emission by 29.3–38.2% Direct physical recycling reduces water consumption by 30.1–41.2% Provincial analysis reveals potential water-carbon conflicts in remanufacturing LIBs [ABSTRACT FROM AUTHOR]

Electricity transmissions have been utilized in China to balance its spatially mismatched development needs and natural resources endowments. However, it has led to spatial shifts of negative environmental impacts induced by electricity generations, including water consumption and carbon emissions. This study calculates that, from 2010 to 2016, carbon emissions and water consumption to produce the transmitted electricity have grown from 507 Mt and 2.7 km3 respectively to 642 Mt and 6.5 km3. Applying a structural decomposition model coupled with a Quasi-Input-Output model to quantify the driving factors of such increases, we find that GDP increase has played the dominant role in driving the increase of both factors. Our results also highlight the potential conflicts between carbon reduction and water conservation in developing future electricity transmission infrastructure systems. Changing the electric power sector's energy portfolio and the transmission structure by increasingly utilizing hydropower productions have both contributed to national total carbon emissions reductions, but at the expenses of increased national water consumption. As a result, on a national level, in 2016, due to the inter-provincial differences in energy portfolios and technologies, electricity transmissions have led to 155.27 Mt of net carbon reduction and 3.4 km³ of additional net water consumption compared to the counterfactual scenario where no electricity transmission were facilitated. The future expansion of electricity transmission network needs to consider such trade-offs, particularly within the contexts of global climate change mitigation and emergent challenges posed by water stresses. Image 1 • Carbon emitted and water consumed for China's power transmission have increased. • 642 Mt carbon emitted and 6.5 km³ water consumed for China's power transfers in 2016. • Changing generation and transmission structures reduce carbon but increase water. • Power transmissions led to 155.27 Mt of national net carbon reduction in 2016. • Power transmissions led to 3.4 km³ of national net water consumption increase. [ABSTRACT FROM AUTHOR]